There's a new kid on the block that many say sounds more realistic than VB-3.
GG AUDIO's Blue3.
The VB-3 was my go-to hammond organ, before that it was Native Instruments B4-II
I have many other Hammond emulators, all offer slightly different sounds.
My one gripe about Blue3 is that it doesn't have a very loud bottom end (which I'm told is realistic and being true to a real Hammond B3.) But when I do a gliss (a hand-slide up the keyboard), the VB-3 really comes through, with a loud booming, grumbling bottom end bass sound, that makes the gliss stand out and cut through the other instruments.
But other than that the Blue3, is much more bright sounding, and the mid and high keys cut through the other instruments. Some say a few of the presets sound a bit too "synthy", but there are a lot more controls and fine tuning available, along with different tonewheel sets and a choice of speakers. The Blue3 also has a better Leslie speaker sound.
You can download the Blue3 demo at:
http://www.gg-audio.com/